Low back pain accounts for 1.2 million disabled persons in the USA and the number is increasing at an alarming rate. 40-100 laminectomies and disc excisions are done per 100,000 persons per year. However, there are very few randomized controlled trials (RCT) regarding the efficacy of treatments for low back pain, and only a handful of RCTs regarding degenerative spondylolisthesis. The purpose of this study, therefore, is to conduct a double blind RCT of treatments for degenerative spondylolisthesis and spinal stenosis. This is a condition primarily affecting the elderly. The study will compare the effectiveness of grafting after decompression (with or without internal fixation) with conservative treatment. The internal fixation will be accomplished with a pedicle screw fixation system. The conservative case will include NSAIDs, corset (as needed), aerobic training, and trunk strengthening. The application initially proposes to overcome the frequent problem of inadequate recruitment by means of a prerandomized design in which the patient is randomized to a treatment group (surgery or not) before being asked to consent to the assigned treatment. Parenthetically, a revision, submitted later, changed this to a classical randomization design because it is believed to raise less ethical concerns. Preliminary surveys have indicated to the team that recruitment of a sufficient number of patients will not be a problem. The type of surgery (fusion with pedicle fixation or fusion without pedicle fixation) will be randomized at the time of surgery. The main outcomes of the study will be a comparison between treatments of pain relief and objective measures of disability. Assessments will be made at baseline, and at 3, 6, 9, 12 and 24 month intervals for most of the survey instruments, and at baseline and at 12 months for the PT evaluation. Radiographic examination will be conducted at baseline and at 12 months. The primary outcomes are a change of range of motion, maximum voluntary effort, Sorenson (time and median frequency shift), muscle response time, and Roland Disability Questionnaire score. The secondary outcomes are defined as the ordinal scales of pain, motor and sensory symptoms, patient overall global transition, SF36 (HSQ), radiographic score on plane films, MRI and CT. Other measured variables are medication use and surgical intervention during follow- up. The study will also compare each treatment in terms of total cost, in cost per day of morbidity saved, and cost benefit. Both direct and indirect costs will be included. Potential predictors of response to surgery such as gender, age, smoking history, combined conditions and clinical history of back problems will also be assessed.